Process for recovering precious metals.



I. A. WISWELL.

PROCESS FOR REOOVERING PRECIOUS METALS.

APPLIOA'IIOH TILED FEB.11 ,1914.

LlfiQl'ifi. Patented Dec. 8, 1914.

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F. A. WISWBLL.

3300388 FOR BEOOVERING PRECIOUS METALS.

APPLIOATION TILED FEILll, x914.

1 9 1 $0, 1 W5 a Patented Dec. 8, 1914.

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ll'll MI 3 I. A. WISWELL.

PROCESS FOR RBCOVERING PRECIOUS METALS.

APPLICATION FILED rm.11,1914.

1 J$U,1?5, Patented Dec.8,1914.

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F. A. WISWELL.

moonss FOB RBGOVEEING PRECIOUS METALS. APPLICATION FILED IEB.11, i914.

Patented Dec. 8, 1914.

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FREDERICK A. WISWELL, 01* OAKLAND, CALIFORNIA.

PROCESS F013, RECOVEKELING PRECIOUS METALS.

Specification of Letters Patent.

me ias.

Application filed February M, 191%.

To all whom it may concern:

.Be it known that I, Fimnnmon A. \VJswnLL, a citizen of the United States, residing at Oakland, in the county of Alameda and State o't Californla, have invented certain new and useful Improvements in Processes for Recovering Precious Metals, of which the following is a specification.

My invention relates to an improved process for extracting and recovering preferably precious metals, such as gold and platinum 'i'romsand, gravel or finely divided or pulverized ores containing them by the use of mercury, in the form of a mercury salt, or metallic mercury, or both, with or without the aid oi. an externally ob tained electric current.

It is well known that gold contained in sand, gravel or pulveriacd or finely divided ores or rock, as well gold and platinum in placer deposits, frequently occur in such minute particles as to make their recovery exceedingly difficult, expensive, and oftcntimes impossible by the ordinary processes of amalgamation, heretofore emploved. The ores of gold and platinum are often o 1 so low a per cent. oi metal to the ton of the rock, sand, gravel or the like, that the ordinary smelting processes cannot be carried out profitably. It has also been found that not infrequently the processes of chlorination and cyanidation are too costly for profitable operation of such low grade ores or the like. It is also a well known fact that processes ordinarily employed for car rying out such processes are generally so costly that they cannot be installed where small capital is available.

An important object of this invention is to provide a process of the above mentioned character. which may be ad 'antageously employed to recover precious metals, par-- ticularly gold and platinum, from sand. gravel or finely divided or pulverized ores, containing the precious metals in a finely divided state, whereby their recovery will be highly profitable, and the apparatus required to carry out the process will not be too expensive.

A further object of the invention is to provide a proces of the above mentioned character, whereby platinum may be extracted ;firom sand, gravel, or pulverized or finely divided ores, containing gold and. platinum in a finely divided state, where it tail view (if a contact.

Patented Dec. d, 11.91%,

Elelifll no. maoei.

dinal sectional view through the apparatus,

taken on line l-1 of Fig. 2, Fig. 2 a plan view of the same, Fig. 3 is a. horizontal sectional view taken on line 3-43 of Fig. 1, Fig. l is an elevatmn of one end of the a p paratus, l ig. is a side elevation of the mercury salt treating ainalgamator, ineluded in the apparatus, Fig. (3 is a central longitudinal sectional view through the same. Fig. 7 is a side elevation of a. rotata blc drum included in the same, Fig. 8 is a transverse sectional view taken on line 88 of Fig. 7, Fig. 9 is a. similar view taken on line 9--9 of Fig. 6, Fig. 10 is a fragmentary central longitudinal section taken through 1 slightly difl'ercut form of mercuric salt treating amalgamator, Fig. 11. is a transverse sectional View taken on line ll ll of Fig. 10. Fig. 12 is a similar view taken on line ]2-l2 of Fig. 10, and Fig. 13 is a do I will first describe the apparatus which may be advantageously employed tor carryinn out my process.

The numeral 15 designates an upstanding frame. which may be advantageously 'formod oi wood or the like. Suitably mounted in the upper portion of the upstanding frame 15 is a mercury salt treating: amalgamator, designated as a whole by the numeral 16. lhis mnalgramator, as more clearly shown in Figs. 5, 6, 7 and 8, includes an outer shell 17. which is preferably cylindrical and horizontally arranged. This outer shell is relatively stationary. The outer shell 17 is preferably formed in two parts 18, provided at their contiguous edges with exterior flanges 19. secured together by bolts 20. Suitable packing may be arranged between these flanges so that the shell will 15 clearly illustrated in Figs. 7 and 8.

be air tight. The portions 18 of the shell 17, however, are not insulated from each other, but are electrically connected by the bolts 20, for a reason to be apparent hereinafter.

The shell 17 or parts thereof is preferably formed of iron, although other material may be employed.

liotatably mounted within the shell 17 is a cylindrical drum or cylinder 21, which is 10 preferably formed of iron and rigidly in width outwardly. The shell 17 is pro vided with internally arranged teeth 24, arranged in spaced annular groups, the teeth 20 in each group being spaced. The teeth 24 are arranged between the teeth 23, as clearly shown in l ig. 6. Formed upon or connected with the opposite ends of the shell 17 are combined stuffing boxes and hearings, in-

25 eluding outer tubular casings 25, which receive therethrough the driving shaft 22. These casings 25 are provided with chambers for receiving electrical non-conducting packing 26, through which the shaft 22 passes, as shown.

The numeral 27 designates rin s, which engage the packing 26, and are moved toward the sarne by clamping bolts 28.

It is desired that the drum 21 be insulated from the shell 17, and for this purpose insulating material 29 is interposed between the ends of the drum, shaft 22, and the ends of the shell 17, as more clearly shown in Fig. 6. Tnsulating material 30 is also interposed between the shaft 22 and the rings 27.

As more clearly shown in Fig. 6, the shaft extends axially'through the drum 21, and is rigidly connected therewith by means of transverse pin 29', said drum serving to completely cover and protect the shaft against chemical action. The drum 21 may be removed when desired. This drum is provided at its ends with tapered or conical heads 31, which decrease, in diameter inwardly, serving as guide means for the material being fed into one end of the shell 17 and discharged from the opposite end thereof. The shell' 17 is provided at one end with an enlarged opening, in communication with an inlet pipe 32, carrying a funnel 33 into which a chute-34 discharges, as clearly shown in 1. At its opposite end an outlet pipe leadsinto the shell 17, such outlet pipe being provided with a vertical vent pipe 36, serving to prevent the creation of vacuums wlthin the shell 17, whereby the material will freely pass therethrough. The shaft 22 is rotated by a pulley 37, which is driven from a suitable source of power 55 (not shown).

Arranged near and to one side of the funnel 33 is a supply tank 38, for holding and dissolving mercuric chlorid or other chemicals, the same being discharged into the funnel through aspout 39, as clearly illustrated in Fig. 1.

Attention is now called to Figs. 10, 11, and 12, wherein the shell 17 is shown formed in a single part, with its opposite ends open and closed by plates or heads 10, connected therewith by bolts 11, the heads or plates 40 are thoroughly insulated from the shell 17. The shell 17 is provided with inwardly ex tending teeth 42, preferably of the shape shown in Fig. 12. The drum 21 is of the same construction as hereinabove described, with its teeth 23 operating between the teetl. 42. This drumis driven by the shaft 22, which is insulated from the shell 17 Each plate or head 40 is provided with a chamber for receiving; electrical non-conducting packing 43, held in place by a ring 14, moved inwardly by clamping bolts 15 or the like. The material supply and discharge means for the drum 21 will remain the same.

The numeral designates (see more particularly Figs. 5, 6 and 10) a wire, having: connection with one pole of a source of electric current (not shown), such wire being electrically connected with the shell 17 by a binding post 47. A wire 18, electrically connected with ti e opposite pole of the source of current, is connected with suitably ipported contact strip or plate 19, (see Fig. 13), having slidable contact with one end of the shaft It is thus seen that the insulated shell 17 and drum 21 are electrically connected with the opposite poles of the source of current for purpose to be hereinafter explained.

testing upon the lower portion of the up standing frame 15 is a stationary upstanding frame 50, upon which is vertically adjustably mounted a supporting frame designated by the numeral 513. The upstanding frame 50 includes four vertical guide standards 51 firmly secured to the frame 50 but slidably fitting into recessed parts or vertical rooms 56 of the adjustable frame 56, as shown in l igs. 2 and 3. thus insuring vertical, central alinement of the frames 50 and 56 with each other while admitting of the latter being raised or lowered. which when suitably iustcd. rests on blocks 55 of desired thickness. Within the frame 56 is. suitably mounted a horizontal thrust plate 57 and lnjnizontally disposed bearings 53 and 59. .llotatably and centrally mounted within the frame 56 is a vertical tubular shaft ($0. receivin material discharged from' the pipe 35. The tubular shaft 60 extends axially within a tank or receptacle 61, which is stationary and suitably connected with the upper end of-the frame 50, as shown. Rigidly mounted upon the lower portion of manure the tubular shaft and arranged for rotation within the receptacle 61 are suitably spaced superposed agitator blades 62, which are horizontally arranged with their upper faces beveled or vertically inclined, whereby they will serve to elevate the ore or material, within the receptacle (i1, when they are rotated in proper direction; The receptacle 61 is partially filled with metallic mercury, for a purpose to be explained. ltigidly connected with the upper portion of the tubular shaft is a horizontal bevel gear 63, the lower end of the hub of which rests on the horizontal bearing plates 57 and supported thereby. It is thus seen that when the horizontal frame 56 is elevated the lower end of the tubular shaft (30 will be moved away from the lower end of the receptacle 61, as will be more fully explained. Rotatably mounted within the bearings 58 and 59 is a horizontal shaft Gel, to the inner end of which is rigidly connccted a bevel gear 65, engaging the bevel gear 63.

The numeral 66 designates a pulley which is rigidly mounted upon the shaft 64-, while the numeral 67 designates a pulley which is rotatably mounted upon the shaft and arranged near the pulley 66. It is thus seen that a belt may be shifted from the pulley 67 to the pulley 66 and vice versa, for retating, and stopping the shaft fhl.

The receptacle 61 is provided near and s 'iac/ed from its upper end with an outlet pipe 68, which discharges into the vertical tubular shaft 60 of apparatus which is iden tical with the apparatus including the tu' bular shaft 00 hereinabove described, for which reason it is thought that no further description of the same is necessary, it being understood that any suitable number of these tll'JPtllullllSGS may be connected in tandem or series, as may be found advantageous.

In the practice of my process in conncction with the apparatus herewith shown and described. the preferably sifted sand, gravel or pulverized ores containing fine particles of the gold, platinum, silver or the like, preferably having water added thereto to form a mass having a pasty consistency, is fed from the chute 3 L to the funnel 33, and passes through pipe 32 into the intake end of the shell 17. An aqueous solution ofa salt of mercury, preferably mercuric chlorid, preferably containing a proper amount of sulfuric acid of the desired strength, is fed from the tank 38 into the funnel 33 and passes therefrom into the shell 17, to engage with the finely divided precious metal con taining material. The shaft is prefer ably "apidly rotated, to effect a corresywnding ro ation of the drum 21, but the speed of rotation of the shaft 22 is to be' detern'iined in vie of the character of the material being treated. I have found that by adding a proper amount of sulfuric acid of suitable strength to the aqueous solution of mercuric chlorid such mercuric chlorid will not be deteriorated by the sulfuric acid but its chemical action will be aided thereby will be more fully explained. The aqueous solution of mercuric chlorid in the presence of the iron of the shell 17 gives up to the latter its hydrochloric acid, due to the strong aliinity that the hydrochloric acid has for iron, said mercuric chlorid simultaneously precipitating metallic mercury, which under the peculiar conditions present during the reaction, will actively combine with the gold or platinum. The peculiar activity of the metallic mercury thus obtained, to amalgamate the precious metals, is due partly to the fact that electric energy is generated during the operation. 'lhe hydrochloric acid which is formed, as above stated, acts much more readily upon the iron of the shell 17 than upon the fine particles of the precious metals, such action being increased when sulfuric acid is added, which is preferred. As a result of this the iron shell, 17 and drum 21 become electropositivc, while the pre eious metals in the mcnstruum, become electic-negative. I have found that gold and platinum particles in. pulverized ores are ideal substances to fulfil the function of the clectro-negative or cathode pole conditions as above stated. The shell 17 and drum 21 are designed and operate to violently agitate the finely divided precious metal carrying material to a degree sutlicient to amalgamate the most minute particles of precious metal, when the same are acted upon by the mercuric chlorid. It is thus seen that within theshell 17 the proc ess of electrolysis is carried out, the iron shell 17 and drum 21 being electro-positive, while the fine particles of gold, platinum. silver or the like are electro-negative, being: the less soluble, whereby the metallic mercury precipitated from the mercuric chlorid will deposit on and amalgamatc with the precious metals. The deposition of the metallic n'lercury occurs by voltaic coupling of 'any of the electrii-chcmically excited parts of the interior of the iron shell 17 and drum 21 with the precious metals, therefore the toothed drum is rapidly rotated. to compel, as near as possible, every part of the passing pulp of precious metal containing material.including. its precious metal particles. to contact with the electro-positive excited parts of the iron shell. As such contact may be, and usually is instantaneous, the quantity of mercury deposited on the particles of precious metal may be comparatively small, particularly when the mercuric chlorid solution is weak. The deposition of the metallic mercury upon the particles of precious metal, as a result of the electrolysis of mercuric chlorid, as above indicated, may be substantially aided by the addition of the sulfuric acid, by reason of its greater action upon the iron material of the shell 17 or drum 21, but at the expense of the more rapid destruction of the latter. In some cases, the ores may carry, in addition to the particles of precious metals, combinations of sulfur or the like metals, that it is not desired to save, such for instance as sulfur, arsenic, antimony, etc. lhe latter are readily soluble inv an acid, such as sulfuric acid in suitable quantity, the affinity of which for arsenic and antimony is much greater than for the iron of the agitating parts. lln such cases, the sulfid arsenic or antimony, solutions thus obtained, if still carrying free acid, instead of contaminating the metallic mercury, tend to purify the same. The addition of the sulfuric acid, properly diluted, to the aqueous solution of mercuric chlorid, in the tank 38, will result in the simple mixture of the two solutions, without deleterious action on either. Such a mixture is regularly fed to the pulp which is being violently agitated within the shell 17, as above stated, while the pulp is being subjected to the action of the chemical solution, formed of an aqueous solution of :mercuric chlorid and sulfuric acid. The chemical solution and ore pulp are preferably subjected to the action of adventitious electric energy or current, the character of which is to be determined in view of the particular character of the material being treated. Either direct or alternating current may be used, but it is preferred to use a direct current having its polarity periodically reversed. As above explained, one pole of the source of current is connected with the drum 21 while the' other pole is connected with the shell 17. Inasmuch as iron and platinum are not susceptible to amalgamation with mercury unalloyed with sodium in the absence of a properly applied adventitious electric cur rent, it is obvious that it is advantageous to use such current, to recover the platinum.

However, it is not desired that the mercury should combine with the iron of the shell 17 or drum 21.

The shell 17 and drum 21 are insulated.

from each other, as described, whereby they will alternate in polarity synchronously with a source of current, having its polarity -periodically or frequently reversed, whereby any tendency to deposit metallic mercury upon the shell 17 or the drum 21 will be instantly succeeded and neutralized by an equal energetic tendency to throw any deposited metal off the same. The suspended particles of gold and platinum, by reason of the violent agitation of the pulp by themeans hereinabove described, and also be.

cause of the well known magnetic effect on such loose metallic particles in such a magrecover the values therefrom. The advantage of employing an alternating current or a direct current having its polarity periodically reversed, will also be apparent by the consideration of the fact that the ores of the metals, such as gold, platinum, silver or the like, not infrequently carry copper ina condition capable of solution in the mercuric chlorid and sulfuric acid menstruum, before mentioned. Under the action of electrolysis, which takes place in the shell 17, as above stated, with the use of a direct current passing continuously in one direction, metallic copper will be deposited on the interior of the shell 17, if that were made the negative pole or on the exterior of the drum 21, if it were made the negative pole. To either of these coppered metallic parts, metallic mercury would adhere, requiring the"appa ratus to be taken apart to remove the copper amalgam. By the use of an alternat ng current or a direct current having its polarity periodically reversed, the copper andmercury will not be deposited upon the shell or drum, .for any tendency to deposit the same thereon when the current has one polarity is repelled when the polarity of the current is reversed. As a result of treating the pulp, as above explained, the fine particles of precious metal, such as gold, and platinum, are combined or coated with the mercury, the pulp carrying the amalgamated particles of precious metals passing through the pipe 35, and into the rotatable tubular shaft 60 to be discharged within the lower portion of the receptacle 6 1, which is partly filled with metallic mercury. lhe blades or agitators 62 are rotated at the proper speed, whereby the pulp is continuouslyv agitated so that the mercury coated,

fine particles of the precious metal maybe absorbed by the quantity of metallic mercury at the bottom of the receptacle 61 and the pulp then passes through pipe 68, to be fed into the tubular shaft 60 of the next apparatus also containing metallic mercuryf be vertically adjusted to move the lower end thereof toward and away from the upper surface of the metallic mercury. As the manner in which the vertical shaft 60 operates has already been described it will not be repeated. The precious metals havin been thus separated from the ore pulp an retained by the metallic mercury baths in the receptacles 61 as hereinbefore described, the now barren pulp flows out through the pipe.68 to waste.

At desired times the mercury, conta'ning its collected amalgamated values, is d awn out from the receptacles 61 and retorted, or otherwise treated by any. of the well known or prepared recesses for se arating the precious metals from the meta lic mercury.

Having described my invention, I claim 1. The herein described process, which consists in subjecting finely divided material containing precious metals in fine particles to the action of an aqueous solution of mercuric chlorid, inthe presence of a metal which is more readily acted upon b the mercuric chlorid than the fine artic es of the precious metal, while Sub ecting the mass to the action of an electric current having its polarity periodically reversed.

2. The herein described process, which consists-in agitating a mixture of finely divided material containing precious metals in fine particles and an aqueous solution of mercuric chlorid and an acid, in the presence of a metal which is more readily acted upon by the aqueous solution of the merin presence of two witnesses.

curic chlorid and acid than the fine par ticles of the precious metal.

3. The herein described process which consists in subjecting finely divided material containing precious metals in fine particles to the action of an a ueous solution of mercuric chlorid and sul. uric acid, in the presence of a metal which is more readily acted upon by the mercuric chlorid and sulfuric acid than the fine particles of precious metals. H

' 4:. The herein described process, which consists in agitating a finely divided material containing precious metals in fine par ticles and an aqueous solution of mercuric chlorid and an acid, inthe presence of iron, substantially as described.

5. The herein described process, which consists in subjecting finely divided material carrying precious metals in fine particles to the action of an aqueous solution of a mercury salt while subjecting the aqueous solution of the mercury salt to the action of electrolysis whereby the fine (particles of precious metal are amalgamate by the me. tallic mercury, and subsequently passing the material containing the amalgamated particles of precious metal into metallic mercury.

In testimony whereof I afiix my-signatur FREDERICK A. WISWELL.- Witnesses:

W. A. STOCK, R. M. OYARZO.

Goplca of this patent may be obtained for fl've cents each, byaddresslng the Commissioner of Patents,

' Washington, D. 0." 

